We are often asked about flexibility. Of course, why else would you require a “flex” board?
“Will the flex board crack if use ED copper on it?’’
Within this article we would like to investigate two different materials (ED-Electrodeposited and RA-rolled-annealed) and observe their impact on circuit longevity. Though well understood by the flex industry, we are not getting that important message to the board designer.
Let’s take a moment to review these two types of foil. Here is the cross-section observation of RA Copper and ED Copper:
Flexibility in the copper comes from multiple factors. Of course, the thinner is the copper, the more flexible the board is. In addition to the thickness (or thinness), copper grain also affects flexibility. There are two common types of copper that are used in the PCB and flex circuit markets: ED and RA as aforementioned.
However, there is no reason to fear ED copper in dynamic applications. On the contrary, it is the de facto choice in thin, lightweight consumer applications requiring high cycle rates. The only concern is careful control of where we use “additive” plating for PTH process. RA foil is the only choice available for heavier copper weights (above 1 oz.) where heavier current applications and dynamic flexing are required.
To understand the advantages and disadvantages of these two materials, it is important to understand the benefits in both cost and performance of these two types of copper foil and, just as important, what is commercially available. A designer needs to consider not only what will work, but whether it can be procured at a price that will not push the end-product out of the market pricewise.
These are the discussion points to review with us or your flex board supplier. Contact them early in the process and make sure they understand your needs. Alternatively, contact us at email@example.com and we will be happy to look at your requirement and discuss further.